1. Field of the Invention
The present invention relates to golf balls. More particularly, the present invention relates to multi piece golf balls having a center, a mid layer and a cover.
2. Description of the Related Art
Golf balls have numerous dimples on the surface thereof. The dimples cause turbulent flow separation through disrupting the air flow around the golf ball during the flight. By causing the turbulent flow separation, a separating point of air from the golf ball shifts backwards leading to the reduction of drag. The turbulent flow separation promotes the differential between upper separating point and lower separating point of the golf ball, which results from the backspin, thereby enhancing a lift force that acts upon the golf ball. The reduction of drag and the enhancement of lift force are referred to as “dimple effect”. Excellent dimples disturb the air flow more efficiently. The excellent dimples achieve great flight distance.
A mold for a golf ball consists of an upper mold half and a lower mold half. Each of the upper mold half and the lower mold half has a hemispherical cavity face. When the upper and the lower mold are mated, a spherical cavity is formed. This mold has a parting line between the upper and the lower mold half. The parting line is a great circle. On a surface of a golf ball, a portion which corresponds to the parting line is referred to as an equator (or a seam). The equator is a great circle. The vicinity of the equator is a particular region. In the vicinity of the equator, dimples tend to be arranged orderly. The orderly arranged dimples deteriorate the dimple effect. JP-A No. 2000-93556 (U.S. Pat. No. 6,066,055) discloses a proposal to remove the particularity in the equator vicinity region.
Flight performance of a golf ball greatly depends on its resilience performance. JP-A No. 10-179799 (U.S. Pat. No. 5,902,192) discloses a golf ball with a core containing aluminum borate whiskers. This golf ball is excellent in resilience performance.
For a golf ball, feel at impact as well as flight performance is important. JP-A No. 2000-70412 (U.S. Pat. No. 6,213,896) discloses a golf ball with a proper amount of compressive deformation. This golf ball is excellent in feel at impact.
Further, durability is also important for a golf ball. JP-A No. 2002-239033 (US No. 2002/0173380) discloses a golf ball with a cover formed by two layers. This golf ball is excellent in feel at impact and durability.
Golf players desire further improvement in performance of golf balls. An object of the present invention is to provide a golf ball which is excellent in flight performance, feel at impact and durability.